sugarmanz/rules_jvm_external

Bazel rules to resolve, fetch and export Maven artifacts

rules_jvm_external

Transitive Maven artifact resolution and publishing rules for Bazel.

Table of Contents

• rules_jvm_external
  • Features
  • Usage
  • API Reference
  • Pinning artifacts and integration with Bazel's downloader
    • Updating maven_install.json
    • Custom location for maven_install.json
    • Multiple maven_install.json files
  • Generated targets
  • Outdated artifacts
  • Advanced usage
    • Fetch source JARs
    • Checksum verification
    • artifact helper macro
    • Multiple maven_install declarations for isolated artifact version trees
    • Detailed dependency information specifications
    • Artifact exclusion
    • Compile-only dependencies
    • Resolving user-specified and transitive dependency version conflicts
    • Overriding generated targets
    • Proxies
    • Repository aliases
      • Repository remapping
    • Hiding transitive dependencies
    • Fetch and resolve timeout
    • Duplicate artifact warning
    • Resolving issues with nonstandard system default JDKs
  • Exporting and consuming artifacts from external repositories
  • Publishing to external repositories
  • Demo
  • Projects using rules_jvm_external
  • Generating documentation

Features

• WORKSPACE configuration
• JAR, AAR, source JARs
• Custom Maven repositories
• Private Maven repositories with HTTP Basic Authentication
• Artifact version resolution with Coursier
• Integration with Bazel's downloader and caching mechanisms for sharing artifacts across Bazel workspaces
• Pin resolved artifacts with their SHA-256 checksums into a version-controllable JSON file
• Versionless target labels for simpler dependency management
• Ability to declare multiple sets of versioned artifacts
• Supported on Windows, macOS, Linux

Get the latest release here.

Prerequisites

• Bazel 4.0.0 and above

Support for Bazel versions before 4.0.0 is only available on rules_jvm_external releases 4.2 or earlier.

Usage

New: on Bazel 6, you can use bzlmod instead of following directions below. See bzlmod. Expect rough edges and incomplete support as bzlmod is still a new feature as of early 2023. Note, bzlmod is expected to be on-by-default in Bazel 7.0.

List the top-level Maven artifacts and servers in the WORKSPACE:

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")

RULES_JVM_EXTERNAL_TAG = "4.5"
RULES_JVM_EXTERNAL_SHA = "b17d7388feb9bfa7f2fa09031b32707df529f26c91ab9e5d909eb1676badd9a6"

http_archive(
    name = "rules_jvm_external",
    strip_prefix = "rules_jvm_external-%s" % RULES_JVM_EXTERNAL_TAG,
    sha256 = RULES_JVM_EXTERNAL_SHA,
    url = "https://github.com/bazelbuild/rules_jvm_external/archive/%s.zip" % RULES_JVM_EXTERNAL_TAG,
)

load("@rules_jvm_external//:repositories.bzl", "rules_jvm_external_deps")

rules_jvm_external_deps()

load("@rules_jvm_external//:setup.bzl", "rules_jvm_external_setup")

rules_jvm_external_setup()

load("@rules_jvm_external//:defs.bzl", "maven_install")

maven_install(
    artifacts = [
        "junit:junit:4.12",
        "androidx.test.espresso:espresso-core:3.1.1",
        "org.hamcrest:hamcrest-library:1.3",
    ],
    repositories = [
        # Private repositories are supported through HTTP Basic auth
        "http://username:password@localhost:8081/artifactory/my-repository",
        "https://maven.google.com",
        "https://repo1.maven.org/maven2",
    ],
)

Credentials for private repositories can also be specified using a property file or environment variables. See the Coursier documentation for more information.

rules_jvm_external_deps uses a default list of maven repositories to download rules_jvm_external's own dependencies from. Should you wish to change this, use the repositories parameter:

rules_jvm_external_deps(repositories = ["https://mycorp.com/artifacts"])
rules_jvm_external_setup()

Next, reference the artifacts in the BUILD file with their versionless label:

java_library(
    name = "java_test_deps",
    exports = [
        "@maven//:junit_junit",
        "@maven//:org_hamcrest_hamcrest_library",
    ],
)

android_library(
    name = "android_test_deps",
    exports = [
        "@maven//:junit_junit",
        "@maven//:androidx_test_espresso_espresso_core",
    ],
)

The default label syntax for an artifact foo.bar:baz-qux:1.2.3 is @maven//:foo_bar_baz_qux. That is,

• All non-alphanumeric characters are substituted with underscores.
• Only the group and artifact IDs are required.
• The target is located in the @maven top level package (@maven//).

API Reference

You can find the complete API reference at docs/api.md.

Pinning artifacts and integration with Bazel's downloader

rules_jvm_external supports pinning artifacts and their SHA-256 checksums into a maven_install.json file that can be checked into your repository.

Without artifact pinning, in a clean checkout of your project, rules_jvm_external executes the full artifact resolution and fetching steps (which can take a bit of time) and does not verify the integrity of the artifacts against their checksums. The downloaded artifacts also cannot be shared across Bazel workspaces.

By pinning artifact versions, you can get improved artifact resolution and build times, since using maven_install.json enables rules_jvm_external to integrate with Bazel's downloader that caches files on their sha256 checksums. It also improves resiliency and integrity by tracking the sha256 checksums and original artifact urls in the JSON file.

Since all artifacts are persisted locally in Bazel's cache, it means that fully offline builds are possible after the initial bazel fetch @maven//.... The artifacts are downloaded with http_file which supports netrc for authentication. Your ~/.netrc will be included automatically. To pass machine login credentials in the ~/.netrc file to coursier, specify use_credentials_from_home_netrc_file = True in your maven_install rule. For additional credentials, add them in the repository URLs passed to maven_install (so they will be included in the generated JSON). Alternatively, pass an array of additional_netrc_lines to maven_install for authentication with credentials from outside the workspace.

To get started with pinning artifacts, run the following command to generate the initial maven_install.json at the root of your Bazel workspace:

$ bazel run @maven//:pin

Then, specify maven_install_json in maven_install and load pinned_maven_install from @maven//:defs.bzl:

maven_install(
    # artifacts, repositories, ...
    maven_install_json = "//:maven_install.json",
)

load("@maven//:defs.bzl", "pinned_maven_install")
pinned_maven_install()

Note: The //:maven_install.json label assumes you have a BUILD file in your project's root directory. If you do not have one, create an empty BUILD file to fix issues you may see. See #242

Note: If you're using an older version of rules_jvm_external and haven't repinned your dependencies, you may see a warning that you lock file "does not contain a signature of the required artifacts" then don't worry: either ignore the warning or repin the dependencies.

Updating maven_install.json

Whenever you make a change to the list of artifacts or repositories and want to update maven_install.json, run this command to re-pin the unpinned @maven repository:

$ bazel run @unpinned_maven//:pin

Without re-pinning, maven_install will not pick up the changes made to the WORKSPACE, as maven_install.json is now the source of truth.

Note that the repository is @unpinned_maven instead of @maven. When using artifact pinning, each maven_install repository (e.g. @maven) will be accompanied by an unpinned repository. This repository name has the @unpinned_ prefix (e.g.@unpinned_maven or @unpinned_<your_maven_install_name>). For example, if your maven_install is named @foo, @unpinned_foo will be created.

Requiring lock file repinning when the list of artifacts changes

It can be easy to forget to update the maven_install.json lock file when updating artifacts in a maven_install. Normally, rules_jvm_external will print a warning to the console and continue the build when this happens, but by setting the fail_if_repin_required attribute to True, this will be treated as a build error, causing the build to fail. When this attribute is set, it is possible to update the maven_install.json file using:

# To repin everything:
REPIN=1 bazel run @unpinned_maven//:pin

# To only repin rules_jvm_external:
RULES_JVM_EXTERNAL_REPIN=1 bazel run @unpinned_maven//:pin

Alternatively, it is also possible to modify the fail_if_repin_required attribute in your WORKSPACE file, run bazel run @unpinned_maven//:pin and then reset the fail_if_repin_required attribute.

Custom location for maven_install.json

You can specify a custom location for maven_install.json by changing the maven_install_json attribute value to point to the new file label. For example:

maven_install(
    name = "maven_install_in_custom_location",
    artifacts = ["com.google.guava:guava:27.0-jre"],
    repositories = ["https://repo1.maven.org/maven2"],
    maven_install_json = "@rules_jvm_external//tests/custom_maven_install:maven_install.json",
)

load("@maven_install_in_custom_location//:defs.bzl", "pinned_maven_install")
pinned_maven_install()

Future artifact pinning updates to maven_install.json will overwrite the file at the specified path instead of creating a new one at the default root directory location.

Multiple maven_install.json files

If you have multiple maven_install declarations, you have to alias pinned_maven_install to another name to prevent redefinitions:

maven_install(
    name = "foo",
    maven_install_json = "//:foo_maven_install.json",
    # ...
)

load("@foo//:defs.bzl", foo_pinned_maven_install = "pinned_maven_install")
foo_pinned_maven_install()

maven_install(
    name = "bar",
    maven_install_json = "//:bar_maven_install.json",
    # ...
)

load("@bar//:defs.bzl", bar_pinned_maven_install = "pinned_maven_install")
bar_pinned_maven_install()

Generated targets

For the junit:junit example, using bazel query @maven//:all --output=build, we can see that the rule generated these targets:

alias(
  name = "junit_junit_4_12",
  actual = "@maven//:junit_junit",
)

jvm_import(
  name = "junit_junit",
  jars = ["@maven//:https/repo1.maven.org/maven2/junit/junit/4.12/junit-4.12.jar"],
  srcjar = "@maven//:https/repo1.maven.org/maven2/junit/junit/4.12/junit-4.12-sources.jar",
  deps = ["@maven//:org_hamcrest_hamcrest_core"],
  tags = ["maven_coordinates=junit:junit:4.12"],
)

jvm_import(
  name = "org_hamcrest_hamcrest_core",
  jars = ["@maven//:https/repo1.maven.org/maven2/org/hamcrest/hamcrest-core/1.3/hamcrest-core-1.3.jar"],
  srcjar = "@maven//:https/repo1.maven.org/maven2/org/hamcrest/hamcrest-core/1.3/hamcrest-core-1.3-sources.jar",
  deps = [],
  tags = ["maven_coordinates=org.hamcrest:hamcrest.library:1.3"],
)

These targets can be referenced by:

• @maven//:junit_junit
• @maven//:org_hamcrest_hamcrest_core

Transitive classes: To use a class from hamcrest-core in your test, it's not sufficient to just depend on @maven//:junit_junit even though JUnit depends on Hamcrest. The compile classes are not exported transitively, so your test should also depend on @maven//:org_hamcrest_hamcrest_core.

Original coordinates: The generated tags attribute value also contains the original coordinates of the artifact, which integrates with rules like bazel-common's pom_file for generating POM files. See the pom_file_generation example for more information.

Outdated artifacts

To check for updates of artifacts, run the following command at the root of your Bazel workspace:

$ bazel run @maven//:outdated

Advanced usage

Fetch source JARs

To download the source JAR alongside the main artifact JAR, set fetch_sources = True in maven_install:

maven_install(
    artifacts = [
        # ...
    ],
    repositories = [
        # ...
    ],
    fetch_sources = True,
)

Checksum verification

Artifact resolution will fail if a SHA-1 or MD5 checksum file for the artifact is missing in the repository. To disable this behavior, set fail_on_missing_checksum = False in maven_install:

maven_install(
    artifacts = [
        # ...
    ],
    repositories = [
        # ...
    ],
    fail_on_missing_checksum = False,
)

Using a custom Coursier download url

By default bazel bootstraps Coursier via the urls specificed in versions.bzl. However in case they are not directly accessible in your environment, you can also specify a custom url to download Coursier. For example:

$ bazel build @maven_with_unsafe_shared_cache//... --repo_env=COURSIER_URL='https://my_secret_host.com/vXYZ/coursier.jar'

Please note it still requires the SHA to match.

artifact helper macro

The artifact macro translates the artifact's group:artifact coordinates to the label of the versionless target. This target is an alias that points to the java_import/aar_import target in the @maven repository, which includes the transitive dependencies specified in the top level artifact's POM file.

For example, @maven//:junit_junit is equivalent to artifact("junit:junit").

To use it, add the load statement to the top of your BUILD file:

load("@rules_jvm_external//:defs.bzl", "artifact")

Full group:artifact:[packaging:[classifier:]]version maven coordinates are also supported and translate to corresponding versionless target.

Note that usage of this macro makes BUILD file refactoring with tools like buildozer more difficult, because the macro hides the actual target label at the syntax level.

Multiple maven_install declarations for isolated artifact version trees

If your WORKSPACE contains several projects that use different versions of the same artifact, you can specify multiple maven_install declarations in the WORKSPACE, with a unique repository name for each of them.

For example, if you want to use the JRE version of Guava for a server app, and the Android version for an Android app, you can specify two maven_install declarations:

maven_install(
    name = "server_app",
    artifacts = [
        "com.google.guava:guava:27.0-jre",
    ],
    repositories = [
        "https://repo1.maven.org/maven2",
    ],
)

maven_install(
    name = "android_app",
    artifacts = [
        "com.google.guava:guava:27.0-android",
    ],
    repositories = [
        "https://repo1.maven.org/maven2",
    ],
)

This way, rules_jvm_external will invoke coursier to resolve artifact versions for both repositories independent of each other. Coursier will fail if it encounters version conflicts that it cannot resolve. The two Guava targets can then be used in BUILD files like so:

java_binary(
    name = "my_server_app",
    srcs = ...
    deps = [
        # a versionless alias to @server_app//:com_google_guava_guava_27_0_jre
        "@server_app//:com_google_guava_guava",
    ]
)

android_binary(
    name = "my_android_app",
    srcs = ...
    deps = [
        # a versionless alias to @android_app//:com_google_guava_guava_27_0_android
        "@android_app//:com_google_guava_guava",
    ]
)

Detailed dependency information specifications

Although you can always give a dependency as a Maven coordinate string, occasionally special handling is required in the form of additional directives to properly situate the artifact in the dependency tree. For example, a given artifact may need to have one of its dependencies excluded to prevent a conflict.

This situation is provided for by allowing the artifact to be specified as a map containing all of the required information. This map can express more information than the coordinate strings can, so internally the coordinate strings are parsed into the artifact map with default values for the additional items. To assist in generating the maps, you can pull in the file specs.bzl alongside defs.bzl and import the maven struct, which provides several helper functions to assist in creating these maps. An example:

load("@rules_jvm_external//:defs.bzl", "artifact")
load("@rules_jvm_external//:specs.bzl", "maven")

maven_install(
    artifacts = [
        maven.artifact(
            group = "com.google.guava",
            artifact = "guava",
            version = "27.0-android",
            exclusions = [
                ...
            ]
        ),
        "junit:junit:4.12",
        ...
    ],
    repositories = [
        maven.repository(
            "https://some.private.maven.re/po",
            user = "johndoe",
            password = "example-password"
        ),
        "https://repo1.maven.org/maven2",
        ...
    ],
)

Note when using bzlmod the syntax in MODULE.bazel is different than shown above.

Artifact exclusion

If you want to exclude an artifact from the transitive closure of a top level artifact, specify its group-id:artifact-id in the exclusions attribute of the maven.artifact helper:

load("@rules_jvm_external//:specs.bzl", "maven")

maven_install(
    artifacts = [
        maven.artifact(
            group = "com.google.guava",
            artifact = "guava",
            version = "27.0-jre",
            exclusions = [
                maven.exclusion(
                    group = "org.codehaus.mojo",
                    artifact = "animal-sniffer-annotations"
                ),
                "com.google.j2objc:j2objc-annotations",
            ]
        ),
        # ...
    ],
    repositories = [
        # ...
    ],
)

You can specify the exclusion using either the maven.exclusion helper or the group-id:artifact-id string directly.

You can also exclude artifacts globally using the excluded_artifacts attribute in maven_install:

maven_install(
    artifacts = [
        # ...
    ],
    repositories = [
        # ...
    ],
    excluded_artifacts = [
        "com.google.guava:guava",
    ],
)

Compile-only dependencies

If you want to mark certain artifacts as compile-only dependencies, use the neverlink attribute in the maven.artifact helper:

load("@rules_jvm_external//:specs.bzl", "maven")

maven_install(
    artifacts = [
        maven.artifact("com.squareup", "javapoet", "1.11.0", neverlink = True),
    ],
    # ...
)

This instructs rules_jvm_external to mark the generated target for com.squareup:javapoet with the neverlink = True attribute, making the artifact available only for compilation and not at runtime.

Test-only dependencies

If you want to mark certain artifacts as test-only dependencies, use the testonly attribute in the maven.artifact helper:

load("@rules_jvm_external//:specs.bzl", "maven")

maven_install(
    artifacts = [
        maven.artifact("junit", "junit", "4.13", testonly = True),
    ],
    # ...
)

This instructs rules_jvm_external to mark the generated target for junit:Junit with the testonly = True attribute, making the artifact available only for tests (e.g. java_test), or targets specifically marked as testonly = True.

Resolving user-specified and transitive dependency version conflicts

Use the version_conflict_policy attribute to decide how to resolve conflicts between artifact versions specified in your maven_install rule and those implicitly picked up as transitive dependencies.

The attribute value can be either default or pinned.

default: use Coursier's default algorithm for version handling.

pinned: pin the versions of the artifacts that are explicitly specified in maven_install.

For example, pulling in guava transitively via google-cloud-storage resolves to guava-26.0-android.

maven_install(
    name = "pinning",
    artifacts = [
        "com.google.cloud:google-cloud-storage:1.66.0",
    ],
    repositories = [
        "https://repo1.maven.org/maven2",
    ]
)

$ bazel query @pinning//:all | grep guava_guava
@pinning//:com_google_guava_guava
@pinning//:com_google_guava_guava_26_0_android

Pulling in guava-27.0-android directly works as expected.

maven_install(
    name = "pinning",
    artifacts = [
        "com.google.cloud:google-cloud-storage:1.66.0",
        "com.google.guava:guava:27.0-android",
    ],
    repositories = [
        "https://repo1.maven.org/maven2",
    ]
)

$ bazel query @pinning//:all | grep guava_guava
@pinning//:com_google_guava_guava
@pinning//:com_google_guava_guava_27_0_android

Pulling in guava-25.0-android (a lower version), resolves to guava-26.0-android. This is the default version conflict policy in action, where artifacts are resolved to the highest version.

maven_install(
    name = "pinning",
    artifacts = [
        "com.google.cloud:google-cloud-storage:1.66.0",
        "com.google.guava:guava:25.0-android",
    ],
    repositories = [
        "https://repo1.maven.org/maven2",
    ]
)

$ bazel query @pinning//:all | grep guava_guava
@pinning//:com_google_guava_guava
@pinning//:com_google_guava_guava_26_0_android

Now, if we add version_conflict_policy = "pinned", we should see guava-25.0-android getting pulled instead. The rest of non-specified artifacts still resolve to the highest version in the case of version conflicts.

maven_install(
    name = "pinning",
    artifacts = [
        "com.google.cloud:google-cloud-storage:1.66.0",
        "com.google.guava:guava:25.0-android",
    ],
    repositories = [
        "https://repo1.maven.org/maven2",
    ]
    version_conflict_policy = "pinned",
)

$ bazel query @pinning//:all | grep guava_guava
@pinning//:com_google_guava_guava
@pinning//:com_google_guava_guava_25_0_android

There may be cases where you want the default pinning strategy, but want one specific dependency to be pinned, no matter what. In these cases, you can use the force_version attribute on the maven.artifact helper to ensure this happens.

maven_install(
    name = "forcing_versions",
    artifacts = [
        # Specify an ancient version of guava, and force its use. If we try to use `[23.3-jre]` as the version,
        # the resolution will fail when using `coursier`
        maven.artifact(
            artifact = "guava",
            force_version = True,
            group = "com.google.guava",
            version = "23.3-jre",
        ),
        # And something that depends on a more recent version of guava
        "xyz.rogfam:littleproxy:2.1.0",
    ],
    repositories = [
        "https://repo1.maven.org/maven2",
    ],
)

In this case, once pinning is complete, guava 23.3-jre will be selected.

Overriding generated targets

You can override the generated targets for artifacts with a target label of your choice. For instance, if you want to provide your own definition of @maven//:com_google_guava_guava at //third_party/guava:guava, specify the mapping in the override_targets attribute:

maven_install(
    name = "pinning",
    artifacts = [
        "com.google.guava:guava:27.0-jre",
    ],
    repositories = [
        "https://repo1.maven.org/maven2",
    ],
    override_targets = {
        "com.google.guava:guava": "@//third_party/guava:guava",
    },
)

Note that the target label contains @//, which tells Bazel to reference the target relative to your main workspace, instead of the @maven workspace.

The dependency that has been overridden is made available prefixed with original_. That is, in the example above, the version of Guava that was resolved could be accessed as @maven//:original_com_google_guava_guava. The primary use case this is designed to support is to allow specific targets to have additional dependencies added (eg. to ensure a default implementation of key interfaces are available on the classpath without needing to modify every target)

Proxies

As with other Bazel repository rules, the standard http_proxy, https_proxy and no_proxy environment variables (and their uppercase counterparts) are supported.

Repository aliases

Maven artifact rules like maven_jar and jvm_import_external generate targets labels in the form of @group_artifact//jar, like @com_google_guava_guava//jar. This is different from the @maven//:group_artifact naming style used in this project.

As some Bazel projects depend on the @group_artifact//jar style labels, we provide a generate_compat_repositories attribute in maven_install. If enabled, JAR artifacts can also be referenced using the @group_artifact//jar target label. For example, @maven//:com_google_guava_guava can also be referenced using @com_google_guava_guava//jar.

The artifacts can also be referenced using the style used by java_import_external as @group_artifact//:group_artifact or @group_artifact for short.

maven_install(
    artifacts = [
        # ...
    ],
    repositories = [
        # ...
    ],
    generate_compat_repositories = True
)

load("@maven//:compat.bzl", "compat_repositories")
compat_repositories()

Repository remapping

If the maven_jar or jvm_import_external is not named according to rules_jvm_external's conventions, you can apply repository remapping from the expected name to the new name for compatibility.

For example, if an external dependency uses @guava//jar, and rules_jvm_external generates @com_google_guava_guava//jar, apply the repo_mapping attribute to the external repository WORKSPACE rule, like http_archive in this example:

http_archive(
    name = "my_dep",
    repo_mapping = {
        "@guava": "@com_google_guava_guava",
    }
    # ...
)

With repo_mapping, all references to @guava//jar in @my_dep's BUILD files will be mapped to @com_google_guava_guava//jar instead.

Hiding transitive dependencies

As a convenience, transitive dependencies are visible to your build rules. However, this can lead to surprises when updating maven_install's artifacts list, since doing so may eliminate transitive dependencies from the build graph. To force rule authors to explicitly declare all directly referenced artifacts, use the strict_visibility attribute in maven_install:

maven_install(
    artifacts = [
        # ...
    ],
    repositories = [
        # ...
    ],
    strict_visibility = True
)

It is also possible to change strict visibility value from default //visibility:private to a value specified by strict_visibility_value attribute.

Accessing transitive dependencies list

It is possible to retrieve full list of dependencies in the dependency tree, including transitive, source, javadoc and other artifacts. maven_artifacts list contains full versioned maven coordinate strings of all dependencies.

For example:

load("@maven//:defs.bzl", "maven_artifacts")

load("@rules_jvm_external//:defs.bzl", "artifact")
load("@rules_jvm_external//:specs.bzl", "parse")

all_jar_coordinates = [c for c in maven_artifacts if parse.parse_maven_coordinate(c).get("packaging", "jar") == "jar"]
all_jar_targets = [artifact(c) for c in all_jar_coordinates]

java_library(
  name = "depends_on_everything",
  runtime_deps = all_jar_targets,
)

Fetch and resolve timeout

The default timeout to fetch and resolve artifacts is 600 seconds. If you need to change this to resolve a large number of artifacts you can set the resolve_timeout attribute in maven_install:

maven_install(
    artifacts = [
        # ...
    ],
    repositories = [
        # ...
    ],
    resolve_timeout = 900
)

Ignoring empty jars

By default, if any fetched jar is empty (has 0 bytes) the corresponding artifact will still be included in the dependency tree.

If you would like to avoid such artifacts, and treat jars that are empty (i.e. their checksum equals the checksum of an empty file) as if they were not found, you can set the ignore_empty_files attribute in maven_install to remove such artifacts from coursier's output:

maven_install(
    artifacts = [
        # ...
    ],
    repositories = [
        # ...
    ],
    # ...
    ignore_empty_files = True
)

This option may be useful if you see empty source jars when fetch_sources is enabled.

Duplicate artifact warning

By default you will be warned if there are duplicate artifacts in your artifact list. The duplicate_version_warning setting can be used to change this behavior. Use "none" to disable the warning and "error" to fail the build instead of warn.

maven_install(
    artifacts = [
        # ...
    ],
    repositories = [
        # ...
    ],
    duplicate_version_warning = "error"
)

Provide JVM options for Coursier with COURSIER_OPTS

You can set up COURSIER_OPTS environment variable to provide some additional JVM options for Coursier. This is a space-separated list of options.

Assume you'd like to override Coursier's memory settings:

COURSIER_OPTS="-Xms1g -Xmx4g"

Resolving issues with nonstandard system default JDKs

Try to use OpenJDK explicitly if your machine or environment is set up to use a non-standard default implementation of the JDK and you encounter errors similar to the following:

java.lang.NullPointerException
	at java.base/jdk.internal.reflect.UnsafeFieldAccessorImpl.ensureObj(UnsafeFieldAccessorImpl.java:58)
	at java.base/jdk.internal.reflect.UnsafeObjectFieldAccessorImpl.get(UnsafeObjectFieldAccessorImpl.java:36)
	at java.base/java.lang.reflect.Field.get(Field.java:418)
	at org.robolectric.shadows.ShadowActivityThread$_ActivityThread_$$Reflector0.getActivities(Unknown Source)
	at org.robolectric.shadows.ShadowActivityThread.reset(ShadowActivityThread.java:277)
	at org.robolectric.Shadows.reset(Shadows.java:2499)
	at org.robolectric.android.internal.AndroidTestEnvironment.resetState(AndroidTestEnvironment.java:640)
	at org.robolectric.RobolectricTestRunner.lambda$finallyAfterTest$0(RobolectricTestRunner.java:361)
	at org.robolectric.util.PerfStatsCollector.measure(PerfStatsCollector.java:86)
	at org.robolectric.RobolectricTestRunner.finallyAfterTest(RobolectricTestRunner.java:359)
	at org.robolectric.internal.SandboxTestRunner$2.lambda$evaluate$2(SandboxTestRunner.java:296)
	at org.robolectric.internal.bytecode.Sandbox.lambda$runOnMainThread$0(Sandbox.java:99)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
	at java.base/java.lang.Thread.run(Thread.java:830)

or

java.lang.UnsatisfiedLinkError: libstdc++.so.6: cannot open shared object file: No such file or directory
	at java.base/java.lang.ClassLoader$NativeLibrary.load0(Native Method)
	at java.base/java.lang.ClassLoader$NativeLibrary.load(ClassLoader.java:2444)
	at java.base/java.lang.ClassLoader$NativeLibrary.loadLibrary(ClassLoader.java:2500)
	at java.base/java.lang.ClassLoader.loadLibrary0(ClassLoader.java:2716)
	at java.base/java.lang.ClassLoader.loadLibrary(ClassLoader.java:2629)
	at java.base/java.lang.Runtime.load0(Runtime.java:769)
	at java.base/java.lang.System.load(System.java:1840)
	at org.conscrypt.NativeLibraryUtil.loadLibrary(NativeLibraryUtil.java:52)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
  ...

Exporting and consuming artifacts from external repositories

If you're writing a library that has dependencies, you should define a constant that lists all of the artifacts that your library requires. For example:

# my_library/BUILD
# Public interface of the library
java_library(
  name = "my_interface",
  deps = [
    "@maven//:junit_junit",
    "@maven//:com_google_inject_guice",
  ],
)

# my_library/library_deps.bzl
# All artifacts required by the library
MY_LIBRARY_ARTIFACTS = [
  "junit:junit:4.12",
  "com.google.inject:guice:4.0",
]

Users of your library can then load the constant in their WORKSPACE and add the artifacts to their maven_install. For example:

# user_project/WORKSPACE
load("@my_library//:library_deps.bzl", "MY_LIBRARY_ARTIFACTS")

maven_install(
  artifacts = [
        "junit:junit:4.11",
        "com.google.guava:guava:26.0-jre",
  ] + MY_LIBRARY_ARTIFACTS,
)

# user_project/BUILD
java_library(
  name = "user_lib",
  deps = [
    "@my_library//:my_interface",
    "@maven//:junit_junit",
  ],
)

Any version conflicts or duplicate artifacts will resolved automatically.

Publishing to External Repositories

In order to publish an artifact from your repo to a maven repository, you must first create a java_export target. This is similar to a regular java_library, but allows two additional parameters: the maven coordinates and an optional template file to use for the pom.xml file.

# user_project/BUILD
load("@rules_jvm_external//:defs.bzl", "java_export")

java_export(
  name = "exported_lib",
  maven_coordinates = "com.example:project:0.0.1",
  pom_template = "pom.tmpl",  # You can omit this
  srcs = glob(["*.java"]),
  deps = [
    "//user_project/utils",
    "@maven//:com_google_guava_guava",
  ],
)

If you wish to publish an artifact with Kotlin source code to a maven repository you can use kt_jvm_export. This rule has the same arguments and generated rules as java_export, but uses kt_jvm_library instead of java_library.

# user_project/BUILD
load("@rules_jvm_external//:kt_defs.bzl", "kt_jvm_export")

kt_jvm_export(
  name = "exported_kt_lib",
  maven_coordinates = "com.example:project:0.0.1",
  srcs = glob(["*.kt"]),
)

In order to publish the artifact, use bazel run:

bazel run --define "maven_repo=file://$HOME/.m2/repository" //user_project:exported_lib.publish

Or, to publish to (eg) Sonatype's OSS repo:

MAVEN_USER=example_user MAVEN_PASSWORD=hunter2 bazel run --stamp \
  --define "maven_repo=https://oss.sonatype.org/service/local/staging/deploy/maven2" \
  --define gpg_sign=true \
  //user_project:exported_lib.publish`

Or, to publish to a Google Cloud Storage:

bazel run --define "maven_repo=gs://example-bucket/repository" //user_project:exported_lib.publish

Or, to publish to an Amazon S3 bucket:

bazel run --define "maven_repo=s3://example-bucket/repository" //user_project:exported_lib.publish

Or, to publish to a GCP Artifact Registry:

bazel run --define "maven_repo=artifactregistry://us-west1-maven.pkg.dev/project/repository" //user_project:exported_lib.publish

When using the gpg_sign option, the current default key will be used for signing, and the gpg binary needs to be installed on the machine.

IPv6 support

Certain IPv4/IPv6 dual-stack environments may require flags to override the default settings for downloading dependencies, for both Bazel's native downloader and Coursier as a downloader:

Add:

• startup --host_jvm_args=-Djava.net.preferIPv6Addresses=true to your .bazelrc file for Bazel's native downloader.
• -Djava.net.preferIPv6Addresses=true to the COURSIER_OPTS` environment variable to provide JVM options for Coursier.

For more information, read the official docs for IPv6 support in Bazel.

Demo

You can find demos in the examples/ directory.

Projects using rules_jvm_external

Find other GitHub projects using rules_jvm_external with this search query.

Developing this project

Verbose / debug mode

Set the RJE_VERBOSE environment variable to true to print coursier's verbose output. For example:

$ RJE_VERBOSE=true bazel run @unpinned_maven//:pin

Tests

In order to run tests, your system must have an Android SDK installed. You can install the Android SDK using Android Studio, or through most system package managers.

$ bazel test //...

Installing the Android SDK on macOS

The instructions for installing the Android SDK on macOS can be hard to find, but if you're comfortable using HomeBrew, the following steps will install what you need and set up the ANDROID_HOME environment variable that's required in order to run rules_jvm_external's own tests.

brew install android-commandlinetools
export ANDROID_HOME="$(brew --prefix)/share/android-commandlinetools"
sdkmanager "build-tools;33.0.1" "cmdline-tools;latest" "ndk;21.4.7075529" "platform-tools" "platforms;android-33"
export ANDROID_NDK_HOME="$ANDROID_HOME/ndk/21.4.7075529"

You can add the export ANDROID_HOME to your .zshrc or similar config file.

Generating documentation

Use Stardoc to generate API documentation in the docs directory using generate_docs.sh.